At least 28 students and a teacher were killed when a shell hit a school outside the Syrian capital, Damascus, state media and activists say.

The official Sana news agency said the Batiha school in the al-Wafidin camp, about 20km (15 miles) north-east of the capital, was hit by rebel mortar fire.

However, the rebels blamed government forces for the deaths.

Fighting around Damascus has recently intensified, with a BBC correspondent saying the city is coming under siege.

Troops have been attempting to push back rebels from eastern parts of the countryside around the capital, known locally as the Ghouta.

The Wafidin camp is home to about 25,000 people displaced from the Golan Heights, which were captured by Israel during the 1967 war.

"It's a terrorist attack on educational institutions and on students," Hassan Mohsen, head of the Quneitra education department, told the Associated Press. Quneitra is in a Syrian-controlled part of the Golan Heights.

The Syrian Observatory for Human Rights, a UK-based activist group, said there had been battles on Tuesday at a checkpoint near the motorway leading to the international airport, which lies to the south-east.

The Local Co-ordination Committees, an opposition activist network, reported that at least 40 people arrested at a checkpoint on the airport road had been executed by government forces and found by residents of al-Bahdaliya, a village near the suburb of Qabr al-Sitt.

The LCC put the nationwide death toll for Tuesday at 141, including 95 people in Damascus and its suburbs, and 15 in the central city of Homs.

Activists say more than 40,000 people have been killed since the uprising against President Assad began in March 2011.